Induction-motor



R. H. POOL AND G. A. HUGHES.

INDUCTION MOTOR. nrrucmou FILED JULY 10. 1911.

1 22,264. Patented Nov. 18, 1919.

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[Horne UNITED STATES PATENT OFFICE.

ROBERT E. POOL AND GBOVEB A. HUGHES, OF YOUNGSTOWN, OHIO.

INDUCTION-MOTOR.

Specification of Letters Patent.

Patented Nov. 18, 1919.

Application filed July 10, 1917. Serial No. 17?,654.

To all whom it may concern:

Be it known that we, ROBERT H. Poor. and Gnovnn A. HUGHES, citizens of the United States of America, and residing at Youngstown, county of Mahoning, State of Ohio, have invented certain new and useful Improvements in Induction-Motors, of which the following is a specification.

Our invention relates to alternating current motors of the induction type.

The object of our invention is to construct such motors with novel and simple means for automatically regulating the primary current and the torque exerted by the rotating element in response to the torque exerted b the rotating element.

Anot er object of our invention is to construct such motors so that they will automatically respond to the overloads of short duration with an increased torque, and at the same time limiting the primary current of'the motor. Thus it is especially applicable to any machine where an overload of short duration is a art of the cycle of o eration, or where suc overloads are liab e to occur.

In carryin out our invention we use a secondary winding of the ordinary type, carried on a core of laminated magnetic material which turns freely on the shaft of the motor.

The secondary winding and core are held to their position on the shaft by means of a torque responsive device as shown in the accompanying drawings.

The secondary leads are connected. to contact bars set in cylindrical form, with an interior or radial contact surface, and are short circuited by means of brushes making contact with the interior or radial surface of the bars.

The brush holder is rigidly secured to the shaft of the motor. A resistance winding mounted in the rotating element is connected to the contact bars in such a manner that, when the torque exerted changes the position of the brushes, the resistance is inserted in the secondary circuit of the motor.

The secondary circuit of an induction motor should possess a relatively high resistance in order to produce a satisfactory starting, accelerating, and overload torque, but should possess a relatively low resistance for satisfactory normal operating characteristics. Numerous constructions of secondary elements have heretofore been devised for imparting to the winding a relatively high eflective resistance during the starting and accelerating speeds of the motor, and a relatively low efl'ective resistance when the motor reaches near full load speed. Our inventlon contemplates improved and novel means for automatically varying with the torque of the motor the effective resistance of the secondary winding, thus improving the operating characteristics of the motor during overload periods as well as during starting and accelerating periods.

The accompanying drawings set forth the nature of our invention and some of the forms of construction which may be employed.

I igure 1 is a diagrammatic sectional view of an induction motor embodying the feature of our invention. Fig. 2 1s a diagrammatic view of the torque responsive device. Fig. 3 is a diagram showing form of assembled contact segments and connection of internal resistance thereto. Fig. 4. is a diagrammatic view of the short circuiting device in its normal position with reference to the contact bars. 'Fig. 5 is a fragmental view showing a form ofbrush arm construction of centrifugal type.

In Fig. 1 of the drawings we have illustrated our invention embodied in an induction motor of the phase wound secondary type. The working currents of the motor are induced in the secondary winding 13 by a primary or inducing winding 14. The several leads of the secondary winding are connected to the segments a, b, a, of Fig. 3. The segments are assembled as shown in Figs. 3 and 4 in cylindrical form with an interior contact surface. These segments are held in position by an extension of the rotor frame 15 forming a seat, and the ring 11 secured to the frame extension.

The secondary Winding 13 is mounted on a core of laminated magnetic material 12 rigidly secured to the casting or equivalent 15 which is rotatably mounted on a rotatably mounted shaft 25.

o casting 15 is rigidly secured the member 16 which is a part of the torque controlled regulating device. Another member of this device 17 is rigidly secured to the shaft 25.

The casting 15 is thus held to a partial rotation on the shaft by the springs 22 and 23 as shown in Fig. 2.

The brush holder 5 carrying the short cir- (:uiting brushes 6, 7 and 8 is rigidly secured to the shaft 25. The resistance 9 1s mounted in the rotor frame and connected to the segments as shown in Fi 3.

In Fig. 2 oi" our drawings we have illustrated the torque responsive device which holds the secondary winding and its adjuncts to a partial rotation on the shaft. The arms 18 and 19 which-are apart of member 16 are arrnn ed so that their cenicrs will align with 1 1e centers of the arms 20 and 21 which are a part of member 17. The two ends of the open ring 24 are rigidly secured in the arms 18 and 19 and pass freely through the arms 20 and 21 and serve to hold the springs 22 and 23 in their positions between the arms or the members 16 and 17.

Fig. 3 shows the method of assembling the contact segments and the connection thereto of the resistance 9. Fig. 4 shows the short circuiting device consisting of the brush holder 5 and the brushes 6, 7 and 8 and their position with reference to the contact segments when the motor is idle. It will be noted that the segments a, b and c are of varied sizes so that no two brushes pass a division at the same time, Fig. 5 shows a form of centrifugal brush in its position when the rotor is at rest, the brush 26 being held away from the contact bars by the spring 27 which also acts as a current carryingshunt. As the rotor acquires speed, the-brush is thrown out and held against the bars by centrifugal force, the operationof the motor being then the same as with the brush construction shown in Fig. p

The spriii pressure between the two members of t e torque responsive device is such that at normal load the brushes 6, 7, and 8 still make contact with segments a, b, and c which are connected respectively to the secondar leads. The secondary winding is thus s ort circuited through -the brushes and brush-holder and the secondary circuit is'of combarativeiy lowresis'tance as is desired for satisfacto operation. at ormeland light loads. w iien the load on he nibtor' increases, the throne exerted compresses"the spring22 or '23 (dejcei'idi'nl the direction of rotation) causin the ort oil-editing brushes to inove over e contact segments, first shittin to contact a thins cnttingf iiito one "leg of he secondary circuit a portion of -'the"1iiternal resistance 9 A. further increase of torque will break contact with 6 thus inserting resistance into a sec ond leg of the seoondar winding. A third step, when the brush reaks contact with C, inserts resistance into the third leg of the secondary winding. Thenextstepailds resistance in the first leg of the secondafit y winding as the brush passes from a? to As the torqiie is increased, the slibrt circuiting brushes rotate farther on the contact segmr nts, cutting in resistance step "by step as the brushes pass from segment to segment, the last step being when the brush passes from G to 0 the short circuiting device being out of the circuit and the entire resistance 9 is in the secondary circuit.

In starting, the high torque exerted com presses the spring 22 or 23 and rotates the brushes to their last position. As the rotor comes up to speed and the torque diminishes, the spring gradualLy forces the rotor 7 back to its normal position, the brushes movin back to their normal position short circu'iting the segments a, b and 0. Thus we have the relatively high ohmic resistance in' the secondary winding durin startin accelerating and overload perios that is desired for satisfactory operation, and that resistance being automatically varied with the torque exerted.

Obviously, changes may be made in the form and arrangement of the parts without departin from the spirit of our invention, and we I 0 not limit ourselves to the particular construction shown.

Having thus described our invention, what We claim is 1. A :motor of the alternating current induction type "provided 'with a regulating device, comprising means r f onsive 'to the torqiie of the motor, self c6 taihed within the rotating member, whereby the torque of the is regulated.

2. In a motor of 'the alternating current induction type, a retafiizigimehiber coiiiprising a secondary member of the phase wound type, a selfcontained resistance in circuit with said secondary'member, and means responsive to the torque whereby said resistance in circuit with the motor is varied.

3. In a motor of the alternating current induction type, the combination with a sec ondary win" ing of the phase ound type, of a self-contained res'istancein the secondary circuit, a regulating device comprising contact segments moiinted in proximity to the secondary 'windiii. and connected thereto and means opera ifvly related to said contact "ac" eats, jfor varying said resistance, self chntained in motbr aiid'responsive "to the tor he of 'the motor.

4. In a motor 0 the alternatin current induction type thecombination Wlh a. rotatably mou t I s aft, a core of magnetic material mounted hereon,'and a secondary witidin of the ghasewound t pe on said 120 core, 0 a reg-Illa rig device co n rising conta'ct segments mounted in proximity to A the secon'cl'a winding 'and connected thereto, blfiishcs eai ingbn said" contact segments and nrechanical means responsive to the 125 torqiie of. the motorjfor varying the rotative gfqsl gmll of said brnsh'es 'on sai contact seg- 5, 1'1'1' azmrjs'ter af in -names" oii'r'rent indndtihn typeftlna combihation'wit a raw 180 tably mounted shaft, a core of magnetic material mounted thereon, and a secondary winding of the hase wound type on said core,- of a regulating device comprising contact segments and a resistance mounted in the rotating members, said contact segments being secured to the core and connected to the secondary winding and to the resistance, and brushes secured to the shaft, and means self contained in the rotor and operatively related to said brushes and contact segments for varying in response to the torque of the motor and rotative position of said brushes on said contact segments thereby varying the resistance included in the circuit.

6. In a motor of the alternating current induction type, the combination with a rotatably mounted shaft, a core of magnetic material mounted thereon, and a secondary windin of the phase wound type on said core, 0 a regulating device comprisin contact segments secured to the core an connected to the secondary winding, a resistance which is mounted 1n the rotating member and is connected to said contact segments, brushes which are secured to the shaft and bear on said contact segments and mechanical means operatively secured to core and shaft for varying the relative rotation of core and shaft in response and in roportion to the torque of the motor.

n testimony whereof we sign this application.

R. H. POOL. G. A. HUGHES. Witnesses:

HENRY GUGGENHEIM, Roy WEBTOVER. 

